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Related Concept Videos

Mitochondrial Precursor Proteins01:39

Mitochondrial Precursor Proteins

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Mitochondrial precursors are partially unfolded or loosely folded polypeptide chains. Newly synthesized precursors are inhibited from spontaneously folding into their native conformation by the cytosolic chaperones, heat shock proteins 70 (Hsp70), and mitochondrial import stimulation factors (MSFs). Precursors bound to MSFs are guided to the TOM70-TOM37 receptors, while precursors bound to Hsp70  chaperones are targetted to TOM20-TOM22 receptor complexes.
Most of the mitochondrial...
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Mitochondrial Protein Sorting01:39

Mitochondrial Protein Sorting

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Mitochondria are double-membrane organelles of the eukaryotes involved in cellular metabolism, signaling, ATP synthesis, and programmed cell death.  Each of these processes requires specific proteins and enzymes that must be correctly sorted to the right mitochondrial subcompartment for the proper functioning of the organelle.
Most of these mitochondrial proteins are encoded by the nucleus and imported to the mitochondria as unfolded or loosely folded precursors. Mitochondrial precursors...
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Translocation of Proteins into the Mitochondria01:19

Translocation of Proteins into the Mitochondria

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Mitochondrial precursors are translocated to the internal subcompartments via independent mechanisms involving distinct protein machineries called translocases.
Sorting of outer membrane proteins:
Mitochondrial outer membrane proteins are of two types: the transmembrane, beta-barrel porins, and the membrane-anchored, alpha-helical proteins. Beta-barrel porin precursors are translocated by the TOM complex and inserted into the outer mitochondrial membrane by the SAM complex. In contrast,...
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Porin Insertion in the Outer Mitochondrial Membrane01:12

Porin Insertion in the Outer Mitochondrial Membrane

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Porins are beta-barrel proteins translocated to the mitochondrial outer membrane through the TOM complex into the intermembrane space. Porin precursors bind TIM chaperones within the intermembrane space and are guided to the Sorting and Assembly Machinery complex or SAM complex on the outer mitochondrial membrane.
Three models describe the assembly of porins by the SAM complex and their insertion into the outer membrane. Model 1 suggests that porins are assembled outside the SAM channel as the...
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Structure of Porins01:21

Structure of Porins

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Mitochondria, chloroplasts, and gram-negative bacteria have transmembrane, beta-barrel proteins called porins to mediate the free diffusion of ions and metabolites across the membrane. Mitochondrial porin precursors contain conserved amino acid sequences called beta signals at their C-terminal. Beta signals have a  motif of PoXGXXHyXHy (Po-Polar, X-Any amino acid, G-Glycine, Hy-LargeHydrophobic), which are crucial for precursor recognition to initiate precursor assembly. Beta-barrel...
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Mitochondrial Membranes01:45

Mitochondrial Membranes

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A single mitochondrion is a bean-shaped organelle enclosed by a double-membrane system. The outer membrane of mitochondria is smooth and contains many porins - the integral membrane transporters. Porins enable free diffusion of ions and small uncharged molecules through the outer mitochondrial membrane but limit the transport of molecules larger than 5000 Daltons. Further, the outer mitochondrial membrane forms a unique structure called membrane contact sites with other subcellular organelles,...
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Imaging and Quantifying Mitochondrial Morphology in C. elegans During Aging
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Prefoldin 2 contributes to mitochondrial morphology and function.

Ismail Tahmaz1, Somayeh Shahmoradi Ghahe1, Monika Stasiak1

  • 1Institute of Biochemistry and Biophysics, Polish Academy of Sciences, PawiƄskiego 5a, 02-106, Warsaw, Poland.

BMC Biology
|September 12, 2023
PubMed
Summary
This summary is machine-generated.

Prefoldin subunits, particularly Pfd2, are crucial for yeast cell survival under heat and respiratory stress. This cytosolic co-chaperone supports mitochondrial function and protein homeostasis, especially during cellular stress.

Keywords:
ChaperoneMitochondriaPfd2/Gim4PrefoldinProteostasisTom70

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Area of Science:

  • Cellular Biology
  • Protein Homeostasis
  • Mitochondrial Biology

Background:

  • Prefoldin is an evolutionarily conserved co-chaperone of the TRiC/CCT complex, involved in folding newly synthesized cytoskeletal proteins.
  • Its function extends to maintaining protein homeostasis, particularly under cellular stress conditions like mitochondrial dysfunction.
  • Prefoldin operates independently of ATP, making it suitable for stress environments.

Purpose of the Study:

  • To investigate the role of prefoldin subunits in Saccharomyces cerevisiae cell proliferation and survival under various stress conditions.
  • To determine the specific contribution of prefoldin to cellular responses during heat and respiratory stress.
  • To elucidate the connection between prefoldin and mitochondrial function.

Main Methods:

  • Analysis of cell proliferation and survival in Saccharomyces cerevisiae lacking prefoldin subunits under stress.
  • Assessment of mitochondrial morphology and respiratory chain complex abundance.
  • Investigation of prefoldin subunit interactions, specifically Pfd2 with Tom70.

Main Results:

  • Prefoldin subunits enhance cell growth under heat stress.
  • Prefoldin facilitates cell growth under respiratory conditions.
  • The prefoldin subunit Pfd2 supports mitochondrial morphology, respiratory chain complexes, and interacts with the mitochondrial import receptor Tom70.

Conclusions:

  • The cytosolic prefoldin complex is linked to mitochondrial function.
  • Loss of Pfd2 triggers adaptive proteome-level responses, indicating its continuous role in cellular homeostasis.
  • Pfd2 may support mitochondrial function directly via cytosolic quality control or indirectly through the protein homeostasis network.